This invention deals generally with conveyor systems and more specifically with carts moved by an endless chain or towline recessed in the path of the cart and to which the cart is coupled when being moved.
The use of independent carts or other vehicles propelled by a continuously moving towline or chain recessed into a track in the floor is well established in manufacturing and storage facilities. A particular benefit of such systems is that the movement of any cart can be stopped for loading or unloading by disconnecting the cart from the towline and moving it out of the path of the other carts. A common method of coupling the carts to the towline is by the use of a vertically movable coupling pin mounted on the cart. Thus, when the pin is lowered into the recessed floor track and coupled to the towline, the cart moves at the same speed as the towline, and when the pin is raised out of the floor track the cart is stationary.
Typically, the moving towline or chain has coupling fixtures that accept the cart coupling pins and push the pins and the carts along the path. The cart pins are usually manually movable upward out of the floor, and the pins are locked in a high position when disengaged to prevent the pin from inadvertently lowering. When the pins are lowered into the coupling position they are also supported by a fixture on the cart to make the pins accessible for raising.
U.S. Pat. No. 2,816,516 to Diehl shows two notches at the tops of angle bars of different heights, with the higher notch holding the pin in its disengaged position, and the lower notch holding the pin in the position coupling it to the tow chain. U.S. Pat. No. 3,048,126 to Salapatas discloses similar high and low notches in a sleeve to couple and disengage the pin from the towline. U.S. Pat. No. 5,368,152 to Rhodes discloses a pin with a part that rests on the cart frame and lifts the pin out of engagement with the towline when the cart contacts another cart ahead of it.
The problem with all of the prior art coupling pin structures is that they do not accommodate to a cart moving over an uneven surface or even minor obstructions on the supporting surface. All that is necessary to uncouple a cart from the towline is something as mundane as a piece of plywood on the floor over which the cart is moving. In that situation, a cart wheel would move up over the edge of the plywood, but the increased height can lift the coupling pin out of engagement with the towline and stop the cart. Ironically, if the cart included the Rhodes invention described above, the entire production line would soon be brought to a complete halt.
It would be very beneficial to have a coupling pin structure that could accommodate to height variations in the cart support surface and permit the cart to remain coupled to the towline.